Commands tagged Linux (241)

Replace
'/tmp/file 1.txt' '/tmp/file 2.jpg'
with
"$NAUTILUS_SCRIPT_SELECTED_FILE_PATHS"
for Nautilus script
Or with
%F
for Thunar action
If you linking the symlinks itself, but want to link to source files instead of symlinks, use
"`readlink -m "$i"`"
instead of
"$i"
like this:
for i in '/tmp/file 1.txt' '/tmp/file 2.jpg'; do ln -s "`readlink -m "$i"`" "$i LINK"; done
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Show Sample Output

How to figure out what a program is doing.
-tt detailed timestamps
-f also strace any child processes
-v be very verbose, even with common structures
-o write output to file
-s N capture up to N characters of strings, rather than abbreviating with ...

The above is OK if you not worried about security, as per sshpass man pages:
" The -p option should be considered the least secure of all of sshpass's options. All system users can see the password in the command line with a simple "ps" command."
So, instead what I do is use the -e option:
" -e The password is taken from the environment variable "SSHPASS"."
Show Sample Output

I don't like doing a massive sort on all the directory names just to get a small set of them. the above shows a sorted list of all directories over 1GB. use head as well if you want.
du's "-x" flag limits this to one file system. That's mostly useful when you run it on "/" but don't want "/proc" and "/dev" and so forth. Remember though that it will also exclude "/home" or "/var" if those are separate partitions.
the "-a" option is often useful too, for listing large files as well as large directories. Might be slower.

This is just a quick and dirty way to play remote audio files *locally* in your PC.
The best way is to mount the remote Music directory into the local FS, say by using sshfs:
sshfs user@remote:/remote/music/dir/ /mnt/other_pc/

Returns the IP, broadcast, and subnet mask of your interfaces absent any other extraneous info.
I know it's a bit lame, but I've created an alias for this when I *quickly* want to know what a system's IP is. Small amounts of time add up :)
Show Sample Output

Execute commands serially on a list of hosts. Each ssh connection is made in the background so that if, after five seconds, it hasn't closed, it will be killed and the script will go on to the next system.
Maybe there's an easier way to set a timeout in the ssh options...

`mount -o remount` doesn't pick up new NFS options (eg. timeo, soft, retrans, etc) so you need to do a full mount/remount cycle. This one-liner makes it quick and easy :) Update your fstab with the new options, then run it.
Show Sample Output

The lastb command presents you with the history of failed login attempts (stored in /var/log/btmp). The reference file is read/write by root only by default. This can be quite an exhaustive list with lots of bots hammering away at your machine. Sometimes it is more important to see the scale of things, or in this case the volume of failed logins tied to each source IP.
The awk statement determines if the 3rd element is an IP address, and if so increments the running count of failed login attempts associated with it. When done it prints the IP and count.
The sort statement sorts numerically (-n) by column 3 (-k 3), so you can see the most aggressive sources of login attempts. Note that the ':' character is the 2nd column, and that the -n and -k can be combined to -nk.
Please be aware that the btmp file will contain every instance of a failed login unless explicitly rolled over. It should be safe to delete/archive this file after you've processed it.
Show Sample Output

Use as: $ s host1
Will ssh to remote host upon first invocation. Then use C-a d to detatch. Running "s host1" again will resume the shell session on the remote host. Only useful in LAN environment. You'd want to start the screen on the remote host over a WAN.
Adapted from Hack 34 in Linux Server Hacks 2nd Addition.

Use this the next time you need to come up with a reasonably random bitstring, like for a WPA/WPA2 PSK or something. Takes a continuous stream of bytes coming from /dev/urandom, runs it through od(1), picking a random field ($0 and $1 excluded) from a random line and then prints it.
Show Sample Output

This command sets the volume for the main PulseAudio "sink" (usually the ALSA output interface) to the maximum, 100% (the 0x10000 in the command). To set it to an arbitrary volume, replace 10000 with the volume you want times 100 (so 75% becomes 7500).

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again.
That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and
voted up or down.

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted
to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning,
there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.